Hello,
The object is there, but it's implicit:
"Et vous aimez Paris?"
"Oh oui... nous aimons beaucoup Paris!"
Anyway, "aimer" can be used without an object, it's a bit old fashioned but it means "to be in love".
Actually an academic answer would be:
"Et vous aimez Paris?"
"Oh oui... nous l'aimons beaucoup!"
To complete arundhati's answer: aimer = like; aimer beaucoup=adorer= love
And do you like Paris?
ah, yes, we love it